The present invention relates generally to the forming of duct assemblies and more particularly to a duct assembly having an end or intermediate portion which is specifically tailored to the needs of a particular application. The end or intermediate portion may be relatively more flexible and self-forming than the adjoining portion or may have a protective covering to provide the hose assembly with a predetermined characteristic such as abrasion, tear or puncture resistance in a desired area.
Background Art
In the aircraft industry, complex ducts are frequently required for the routing of pressurized fluids, including air, throughout the aircraft. These ducts are often times fabricated in from metal or other rigid materials in several long sections, with each section having numerous branches for coupling various components to the duct. An illustrative duct section constructed in this manner is illustrated in FIG. 1.
Duct section 10 includes a body portion 12 and a plurality of branch portions 14. Body portion 12 and branch portions 14 are formed with relatively expensive tools and equipment according to a design model. The design model typically employs the nominal positions or 3-dimensional location 16 of the components 18 that are to be coupled to the duct section 10, as well as the structure of the device into which duct section 10 is attached, to determine the geometry of the body portion 12 and each of the branch portions 14. In a typical situation, the design data for the duct section 10 that is developed from the design model is quite complex, with many curves, bends and branch portions 14 being formed in the duct section 10 throughout its length.
The configuration of the duct section 10 frequently necessitates that it be fabricated in several component parts which are then coupled together via specialized fittings, clamps or welding. Those skilled in the art will readily understand that due to part-to-part variation between the component parts, as well as the variation in which they are assembled, the configuration of duct section 10 can vary widely from the design model. Complicating matters is that the actual positions 20 of the components 18 that are to be coupled to the duct section 10 frequently vary from their nominal position 16.
If the variance between the actual position 20 of the components 18 and the associated connection point of the duct section 10 are severely mis-aligned, it is necessary to take corrective action, such as modifying the tooling on which the component parts of the duct section 10 are fabricated, modifying the design positions of the components 18 which are connected to duct section 10, and/or reworking duct section 10 to tailor it to the particular application. These corrective actions are frequently expensive and time consuming as it is usually quite difficult to identify and quantify each of the variations from the design model. Often times, the corrective action is iterative in nature, with small improvements being made over an extended period of time.
While the amount of time that is expended to achieve a finalized design is one drawback of an iterative design approach, another concerns the proliferation of components that result from the release of xe2x80x9cintermediatexe2x80x9d versions into production. As each version may have unique servicing and maintenance requirements, thereby increasing the complexity of a servicing program. Furthermore, stocking of several xe2x80x9cintermediatexe2x80x9d versions may be necessary to ensure that all previously produced products may be timely serviced.
One solution that has been proposed is to break the duct section 10 into a plurality of even shorter sub-sections which are coupled together during the installation of duct section 10 into a particular application. One drawback of the use of multiple duct sub-sections is that depending on the particular application, it can be difficult to couple the sub-sections together if the duct sub-sections are relatively inaccessible for servicing after they are located into the application. This solution is also relatively expensive, can adversely affect the overall reliability of the duct section, increase the frequency with which it must be serviced and add considerable weight to the duct section.
These drawbacks are particularly true where relatively long flexible hoses are employed, as these sub-sections tend to move relative to their associated duct-subsections due to vibrations that are generated in the application and transmitted through the duct. This relative motion renders the intersection between the duct sub-sections more susceptible to failure due to the stresses, strain and/or shear forces that are typically created in that region from the clamping device which secures the hose to its associated duct sub-section and/or abrading on another portion of the application (e.g., the structure to which the duct is coupled).
Accordingly, there remains a need in the art for a duct that is relatively easy and inexpensive to fabricate regardless of the complexity of its configuration. The duct should be easy to install and readily accommodate the variation that occurs from part-to-part and application-to-application. Furthermore, the duct should be easily tailored to the unique needs of an application.
In one preferred form, the present invention provides a duct assembly for coupling a pair of components in fluid connection. The duct assembly includes a first portion, a second portion and a support collar. The second portion is relatively more flexible than the first portion and in fluid connection with the first portion. The support collar is coupled to an outer perimeter of the second portion and abuts the first portion. The support collar is sized to prevent the formation of a stress riser at an intersection between the first and second portions to thereby render the intersection less susceptible to tearing in response to repeated flexing of the second portion.
In another preferred form, the present invention provides a duct assembly for coupling a pair of components in fluid connection. The duct assembly includes a duct portion and a sleeve portion. The sleeve portion is bonded to an exterior perimeter of the duct portion in a predetermined area of the duct portion and provides the predetermined area of the duct portion with a predetermined characteristic, such as abrasion and tear resistance.
In another preferred form, the present invention provides a method for forming a reinforced flexible duct assembly. The method includes the steps of providing a duct member, determining a diameter of the duct member, selecting a reinforcement member and a reinforcement pitch based on the diameter of the duct member, and bonding the reinforcement member to an exterior surface of the duct member in a helix such that a pitch of the helix is equal to the reinforcement pitch.
In another preferred form, the present invention provides a method for forming a hose assembly for coupling a plurality of components in fluid connection. The method includes the steps of forming a rigid duct structure and a flexible duct structure; and bonding the flexible duct structure to an end of the rigid duct structure to produce a clampless flexible joint which permits an end of the flexible duct structure opposite the rigid duct structure to be moved relative to the rigid duct structure.
In another preferred form, the present invention provides a method for forming a hose assembly for coupling a plurality of components in fluid connection. The method comprising the steps of forming a flexible duct structure from an elastomeric material; forming first and second rigid duct structures, the first and second rigid duct structures being formed to be relatively more rigid than the flexible duct structure; coupling the first rigid duct structure to a first end of the flexible duct structure; and coupling the second rigid duct structure to a second end of the flexible duct structure such that the flexible duct structure permits the first and second rigid duct structures to be moved relative to one another.